Bob Cratchit is an employee and clerk of Scrooge. Despite only being paid 15 shillings a week (prior to Stave 5) and having minimal heating due to Scrooge refusing to pay for it, he is still grateful to Scrooge for giving him work and accepts his conditions. He represents the idealised working class and is symbolic of the long, underpaid hours that Victorian woking-class people had to endure. He is married to Mrs. Cratchit and has 6 children (Martha, Belinda, Peter, Tiny Tim, and two unnamed children). His son, Tiny Tim, also plays a particularly important role in the play.
As previously mentioned, he symbolises the poor treatment of the Victorian working class by their employers. His name "Bob" is also slang for a shilling, an old unit currency which used to be worth one-20th of a pound, which Dickens may have chosen to present the working class as only being seen for the value of the labuour they produce.
Quotes said by or that describe Bob that you may find useful:
"...that he might keep an eye upon his clerk, who in a dismal little cell beyond, a sort of tank, was copying letters"
"He stopped at the outer door to bestow the greetings of the season on the clerk, who, cold as he was, was warmer than Scrooge"